Injection molding assemblies for molding thermoplastic materials and the like includes a tool unit and a extruder unit including a feed screw. When changing to another thermoplastic material formulation, it is usually necessary to replace the extruder unit and/or feed screw as a result of different geometry requirements of the extruder unit and/or feed screw for such material. Changing of the extruder unit and/or feed screw is cumbersome and time consuming. Depending upon the thermoplastic material formulation, in many instances it is necessary to clean and dismantle the extruder unit prior to processing another thermoplastic material formulation which further increases down time of the injection molding assembly.
In European Patent Application No. 0 069 221, there is disclosed an injection molding assembly provided with a tool unit and two separate extruder units capable of being alternately coupled to the tool unit. In use, when one extruder unit is operatively connected to the tool unit, and thus coupled to the drive of the injection molding apparatus, as well as connected to supply lines therefor, the second extruder unit is disposed in a storage magazine adjacent to the injection molding apparatus. The second extruder unit may be connected to the supply lines when positioned in the storage magazine, to permit the second extruder unit to be maintained at a predetermined temperature level or may be readily brought to operational temperatures before the second extruder unit is substituted for the first extruder unit. The injection molding assembly of the aforementioned European Patent Application does not permit the cleaning of the extruder unit and/or feed screw, and thus cleaning time of the extruder unit is added to the time required for substitution of a extruder unit.
To substitute or exchange a extruder unit, the drive unit and energy supply couplings of the extruder unit connected to the tool unit are disconnected by special actuating means. Thereafter, the extruder unit being exchanged is removed by a crane assembly of three-dimensional capabilities and placed in an appropriate storage magazine. The crane assembly then picks up the second extruder unit in the storage magazine and positions such second extruder unit in operative relationship to the tool unit of the injection molding apparatus, with the drive unit and energy supply couplings being thereafter connected thereto. The injection molding assembly of such aforementioned European Patent Application requires a lot of space, is costly to manufacture and requires a relatively high amount of down time prior to placing the injection molding apparatus into production.